The time zone (hour difference with respect to GMT) is necessary for the calculation of the Legal time
, with respect to the Solar time
used as basis for the solar geometry calculations.
In most cases, the Time Zone value is close to value of the the Latitude/15°.
Usually, it is increased by one unit for "Summer Time", but PVsyst uses to define the "Winter time" only.
For avoiding bad sit definitions, PVsyst fixed a limit of -1 to +2 in the Hidden parameters
, topic "Miscellaneous Meteo, Simulation...".
Some regions (especially in China) need a different Time Zone value; in these cases you have to enlarge these limits.